1. Field of the Invention
The present invention relates to a method for driving a display panel.
2. Description of Related Art
Recently, as thin flat display panels, for example, plasma display panels (hereinafter called xe2x80x9cPDPxe2x80x9d) and electroluminescent display panels (hereinafter called xe2x80x9cELDPxe2x80x9d) have been placed on the market. The light-emitting elements of these PDP and ELDP having only two states, xe2x80x9clight-emittingxe2x80x9d and xe2x80x9cnon-light-emittingxe2x80x9d, whereby halftone drive is effectuated using a sub-field method in order to obtain halftone brightness corresponding to input video signals.
By the sub-field method, an input video signal is converted into N-bit pixel data for each pixel and the display period of one field is divided into N sub-fields corresponding to each of the N-bit bit digits. Each sub-field is assigned a frequency of light emissions corresponding to each of the bit digits of the aforementioned pixel data, respectively. In cases where one bit digit of the aforementioned N bits has, for example, a logic level of xe2x80x9c1xe2x80x9d, light emission is executed for the frequency assigned as mentioned above in the sub-field corresponding to the bit digit. On the other hand, in cases where the aforementioned one bit digit has a logic level xe2x80x9c0xe2x80x9d, no light emission is effected in the sub-field corresponding to the bit digit. According to such a drive method, levels of halftone brightness corresponding to input video signals are expressed by the sum of the frequency of light emissions executed in all sub-fields within the display period of one field.
An object of the present invention is to provide a drive method which can provide an excellent expression a of gray scale in response to the human visual property on a display panel for expressing gray scale using the aforementioned subfield method.
The method for driving a display panel, according to the present invention, is to drive a display panel which forms pixel cells at respective intersections of a plurality of electrode rows and a plurality of electrode columns arranged to intersect said electrode rows; when performing a gray scale drive of said display panel by assigning each of gray scale drive processes of N levels of gray scale that are different from one another in the frequency of light emissions to be executed in one field period to input pixel data based on the brightness of said input pixel data available for expressing the brightness of M levels of a gray scale (M greater than N), the number of said halftone drive processes assigned to low brightness data of said input pixel data is made larger than the number of said halftone drive processes assigned to high brightness data of said input pixel data.